The present invention relates to a process for preparing low emissivity moisture vapor permeable metallized sheets which have superior resistance to corrosion of the metal layer and low emissivity.
Moisture vapor permeable composite sheet products such as fabrics, films or composites thereof having deposited on at least one surface of the sheet a metal layer, e.g. aluminum, and a protective, outer polymeric coating, e.g. acrylate or lacquer, are useful as thermal and electromagnetic radiation barriers in building construction in the form of housewrap or roof lining (also referred to as “construction barrier layers”). When the composite sheet is used as a construction barrier layer, the metal layer reflects infrared radiation and transmits little infrared radiation, providing a thermal barrier that reduces energy loss and keeps the building cooler in the summer and warmer in the winter.
Such metalized sheets allow moisture vapor to pass through the sheet, thus preventing moisture condensation in insulation that is installed behind the sheet, while at the same time providing a barrier to air and liquid water and enhancing the energy efficiency of the building. U.S. Pat. No. 4,999,222 to Jones et al. describes moisture vapor permeable metallized polyethylene sheets having low emissivity prepared by calendering a plexifilamentary film-fibril sheet followed by vacuum metallization. U.S. Pat. No. 4,974,382 to Avellanet describes an infiltration and energy barrier that can be vapor permeable or impermeable having at least one metallized layer thereon. Published PCT International Application No. WO 01/28770 to Squires et al. describes breathable building membranes that include an under layer of microporous film and a top layer formed of a filamentous polymeric fabric, for example a spunbond fabric, which is provided with a moisture vapor permeable reflective metal coating. U.S. Patent Application Publication No. 2003/0136078 to Brown et al. describes a method of insulating a building that includes the step of introducing an insulating membrane comprising a reflective layer and a breathable textile layer into the cavity between the outer cladding layer and the frame. The metallized layer may optionally be coated with a protective layer of plastic or varnish to protect the metal surface.